Method of forming copper wiring in semiconductor device

ABSTRACT

The present invention relates to a method of forming a copper wiring in a semiconductor device. A copper wiring is formed within a damascene pattern. Before a copper anti-diffusion insulating film is formed on the entire structure, a specific metal element is doped into the surface of the copper wiring and the surface of its surrounding insulating film to form a metal element-doping layer. The doped specific metal element reacts with surrounding other elements, due to heat upon depositing the copper anti-diffusion insulating film and a low dielectric constant interlayer insulating film and additional annealing process. For this reason, a copper alloy layer and a metal oxide layer are stacked at the interface of the copper wiring and the copper anti-diffusion insulating film and the metal oxide layer is formed at the interface of the insulating film and the copper anti-diffusion insulating film. The interfacial bondability between the copper anti-diffusion insulating film and each of the copper wiring and the insulating film underlying the insulating film is increased to improve reliability of the wiring.

BACKGROUND

1. Field of the Invention

The present invention relates to a method of forming a copper wiring ina semiconductor device and, more specifically, to a method of forming acopper wiring in a semiconductor device capable of improving reliabilityof the wiring by increasing an interfacial bondability of a copperanti-diffusion insulating film with each of a copper wiring and aninsulating film underlying the insulating film.

2. Discussion of Related Art

Generally, as the semiconductor industry shifts to an ultra large-scaleintegration (ULSI) level, the geometry of the device continues to benarrowed to a sub-half-micron region. In view of improved performanceand reliability, the circuit density is gradually increased. Copper hasa high resistance to electro-migration (EM) since it has a highermelting point than aluminum. Thus copper can improve reliability of thedevice. Further, copper can increase a signal transfer speed since ithas a low resistivity. For this reason, in forming a metal wiring in asemiconductor device, copper has been used as an interconnectionmaterial useful for an integration circuit.

A method of burying copper that may be used currently includes aphysical vapor deposition (PVD) method/reflow method, a chemical vapordeposition (CVD) method, an electroplating method, anelectroless-plating method and the like. Preferred methods of them arethe electroplating method and the CVD method, which have a relativelygood copper burial characteristic.

While copper is used as the material of the metal wiring, a damascenescheme for simultaneously forming a via contact hole for electricalconnection to a lower layer and a trench in which the metal wiring islocated, has been widely used along with the process of forming thecopper wiring in the semiconductor device. A low-dielectric insulatingmaterial having a low dielectric constant is used as the interlayerinsulating film in which the damascene pattern will be formed.

In order to form the copper wiring in the damascene pattern having thevia contact hole and the trench, copper is buried into the damascenepattern through several methods and the buried copper layer is thenpolished by a CMP process, thus making the buried copper layer isolatedfrom neighboring copper wirings.

FIG. 1 is a sectional view for explaining the method of forming thecopper wiring in the semiconductor device according to a prior art.

A first interlayer insulating film 12 and an anti-polishing layer 13 areformed on a substrate 11. The anti-polishing layer 13 and the firstinterlayer insulating film 12 are etched by a damascene scheme to form adamascene pattern 14.

A copper anti-diffusion conductive film 15 is formed along the surfaceof the anti-polishing layer 13 including the damascene pattern 14. Acopper layer is then formed enough to sufficiently bury the damascenepattern 14. Next, the CMP process is performed until the anti-polishinglayer 13 is exposed, thus forming a copper wiring 16 within thedamascene pattern 14. Thereafter, a copper anti-diffusion insulatingfilm 17 and a second interlayer insulating film 18 are formed on theentire structure including the copper wiring 16.

In the above-mentioned method, in order to prevent diffusion of copperelements from the copper wiring 16 to the outside, the copper wiring 16is sealed using the copper anti-diffusion conductive film 15 and thecopper anti-diffusion insulating film 17. In the device having thecopper wiring 16 formed by the conventional method, however, mostdefective wiring generated by electro-migration and stress migrationoccurs at the interface between the copper anti-diffusion insulatingfilm 17 and the copper anti-diffusion conductive film 15, as indicatedby an arrow “A”. This condition is caused by a lack in the interfacialbondability of the copper anti-diffusion insulating film 17 and thelower layers 13, 15 and 16.

SUMMARY OF THE INVENTION

The present invention is directed to a method of forming a copper wiringin a semiconductor device capable of improving electricalcharacteristics and reliability of the device, by increasing aninterfacial bondability of a copper anti-diffusion insulating film andits lower layers to prevent migration of copper elements in a copperwiring.

According to a preferred embodiment of the present invention, there isprovided a method of forming a copper wiring in a semiconductor device,comprising the steps of: forming a first interlayer insulating film andan anti-polishing layer on a substrate; etching the anti-polishing layerand the first interlayer insulating film to form a damascene pattern;forming a copper anti-diffusion conductive film and a copper layer onthe anti-polishing layer including the damascene pattern; forming acopper wiring within the damascene pattern; forming a metal elementdoping layer on the surface of the entire structure including the copperwiring; and forming a copper anti-diffusion insulating film and a secondinterlayer insulating film on the entire structure on which the metalelement doping layer is formed, wherein a copper alloy layer and a metaloxide layer are formed at the interface of the copper wiring and thecopper anti-diffusion insulating film due to heat upon depositing theinsulating film, and the metal oxide layer is formed at the interface oflayers around the copper wiring and the copper anti-diffusion insulatingfilm. At this time, the metal oxide layer may be formed with a uniformthin film, or an unevenness layer having an island shape.

In the aforementioned of a method of forming a copper wiring in asemiconductor device according to another embodiment of the presentinvention, the metal element doping layer is formed by doping a specificmetal element by means of an implantation method or a plasma dopingmethod and is formed by controlling a depth and a concentration of thedoping so that a thickness of the copper alloy layer becomes 10 to 500Å. The specific metal element is a metal element such as Mg, Cd, Be, Snand Pd.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view for explaining a method of forming a copperwiring in a semiconductor device according to a prior art; and

FIGS. 2A to 2C are sectional views for explaining a method of forming acopper wiring in a semiconductor device according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now the preferred embodiments according to the present invention will bedescribed with reference to the accompanying drawings. Since preferredembodiments are provided for the purpose that the ordinary skilled inthe art are able to understand the present invention, they may bemodified in various manners and the scope of the present invention isnot limited by the preferred embodiments described later.

FIGS. 2A to 2C are sectional views for explaining a method of forming acopper wiring in a semiconductor device according to an embodiment ofthe present invention.

Referring to FIG. 2A, a first interlayer insulating film 22 and ananti-polishing layer 23 are formed on a substrate 21. The anti-polishinglayer 23 and the first interlayer insulating film 22 are etched by adamascene scheme to form a damascene pattern 24. A copper anti-diffusionconductive film 25 is then formed along the surface of theanti-polishing layer 23 including the damascene pattern 24. A copperlayer is then formed enough to sufficiently bury the damascene pattern24. Next, a chemical mechanical polishing (CMP) process is performeduntil the anti-polishing layer 23 is exposed, thereby forming a copperwiring 26 within the damascene pattern 24. A specific metal element isdoped into the surface of the first interlayer insulating film 22including the copper wiring 26, thus forming a metal element-dopinglayer 200.

In the above, the first interlayer insulating film 22 is formed using alow dielectric constant in order to solve problems due to parasiticcapacitance between the wirings. For example, the first interlayerinsulating film 22 is formed using materials wherein H, F, C, CH₃, etc.are partially combined in SiO₂ series having a dielectric constant of1.5 to 4.5, organic materials such as SiLK™ product, Flare™ producthaving C—H as a basic structure, and porous materials whose porosity isincreased in order to lower the dielectric constant of the abovematerials.

The anti-polishing layer 23 may be formed using oxide not containingcarbon, or may be formed using silicon nitride and silicon oxynitridecontaining nitrogen or silicon carbide series containing carbon by meansof the chemical vapor deposition (CVD) method so that they can have acopper anti-diffusion characteristic.

The copper anti-diffusion conductive film 25 may be formed by one ofionized PVD TiN, CVD TiN, MOCVD TiN, ionized PVD Ta, ionized PVD TaN,CVD Ta, CVD TaN and CVD WN.

The metal element-doping layer 200 is formed by doping the specificmetal element having a given concentration in a given depth by means ofthe implantation method or the plasma doping method. The specific metalelement is a metal element such as Mg, Cd, Be, Sn and Pd, havingcharacteristics that it is melted in copper in a given concentration ata given temperature to form an alloy, educed in a grain boundary toprohibit migration of the copper elements, and react with a very smallamount of oxygen to form a metal oxide of a fine film quality. The metalelement-doping layer 200 is formed under the condition that theinterfacial bondability can be maximized while minimizing increase inresistivity of the copper wiring due to the specific metal elements. Atthis time, the metal element doping layer 200 is formed by controllingthe depth and concentration of the doping so that the thickness of acopper alloy layer that will be formed later is below 500 Å, preferably10 to 500 Å, more preferably 100 to 400 Å. At this time, theconcentration of the specific metal element doped does not exceed 10%,preferably 0.5 to 10%, more preferably 3 to 8%.

Referring to FIG. 2B, a copper anti-diffusion insulating film 27 isformed on the entire structure on which the metal element-doping layer200 is formed.

In the above, the copper anti-diffusion insulating film 27 is formedover 300 Å in a single layer or multiple layers using one of siliconnitride (SiNx), silicon carbide (SiCx) and silicon nitrocarbide (SiCN),all of which contain a very small amount of oxygen.

Meanwhile, before the copper anti-diffusion insulating film 27 isformed, a plasma treatment is performed in order to remove a copperoxide layer (not shown) generated on the surface of the copper wiring 26while stabilizing the copper wiring 26. In the above, the plasmatreatment may be carried out before the metal element doping layer 200is formed, immediately before the copper anti-diffusion insulating film27 is formed after the metal element doping layer 200 is formed, orbefore and after the metal element doping layer 200 is formed. Theplasma treatment may be performed in-situ while doping the specificmetal element in order to form the metal element-doping layer 200. Suchplasma treatment is performed using a mixed gas of nitrogen and hydrogenor an ammonia series gas at a temperature in the range of 100 to 350° C.

By reference to FIG. 2C, a second interlayer insulating film 28 isformed on the entire structure including the copper anti-diffusioninsulating film 27. An annealing process is then performed so that thespecific metal element of the metal element-doping layer 200 can reactwith surrounding other elements. Accordingly, a copper alloy layer 210and a metal oxide layer 220 are stacked at the interface of the copperwiring 26 and the copper anti-diffusion insulating film 27. The metaloxide layer 220 is formed at the interface of the anti-polishing layer23 and the copper anti-diffusion insulating film 27. Furthermore, themetal oxide layer 220 is formed at the interface of the copperanti-diffusion conductive film 25 and the copper anti-diffusioninsulating film 27.

In the above, it is preferred that the second interlayer insulating film28 is formed using a material of a low dielectric constant if it is amulti-layer wiring structure, in order to solve problems due toparasitic capacitance between the wirings as in the first interlayerinsulating film 22. If it is a single layer metal wiring structure,however, the second interlayer insulating film 28 may be usually formedusing other insulating materials that are used as the interlayerinsulating film of the semiconductor device.

The annealing process is performed over 1 minutes, preferably 10 to 30minutes at a temperature range of 100 to 500° C. Meanwhile, theannealing processes for forming the copper alloy layer 210 and the metaloxide layer 220 are not separately performed, but heat in the process ofdepositing each of the copper anti-diffusion insulating film 27 and thelow dielectric constant interlayer insulating film 28 may be used.

The copper alloy layer 210 is formed as the specific metal element ofthe metal element doping layer 200 are melted in copper elements of thecopper wiring 26 during the annealing process. The metal oxide layer 220that is formed on the copper wiring 26, on the layers 23 and 25 aroundthe copper wiring 26 is formed to have a fine film quality since a verysmall amount of oxygen contained in the copper anti-diffusion insulatingfilm 27 and the specific metal element of the metal element doping layer200 are combined.

As described above, according to the present invention, a copper alloylayer and a metal oxide layer are stacked at the interface of a copperwiring and a copper anti-diffusion insulating film. The metal oxidelayer is formed at the interface of layers around the copper wiring anda copper anti-diffusion insulating film. Thus the interfacialbondability of the copper anti-diffusion insulating film is increased.It is therefore possible to improve electrical characteristics and theyield due to improved reliability of the wiring.

Although the foregoing description has been made with reference to thepreferred embodiments, it is to be understood that changes andmodifications of the present invention may be made by the ordinaryskilled in the art without departing from the spirit and scope of thepresent invention and appended claims.

1. A method of forming a copper wiring in a semiconductor device,comprising the steps of: forming a first interlayer insulating film andan anti-polishing layer on a substrate; etching the anti-polishing layerand the first interlayer insulating film to form a damascene pattern;forming a copper anti-diffusion conductive film and a copper layer onthe anti-polishing layer including the damascene pattern; forming acopper wiring within the damascene pattern; forming a metal elementdoping layer on the surface of the entire structure including the copperwiring; and forming a copper anti-diffusion insulating film and a secondinterlayer insulating film on the entire structure on which the metalelement doping layer is formed, wherein a copper alloy layer and a metaloxide layer are formed at the interface of the copper wiring and thecopper anti-diffusion insulating film due to heat upon depositing theinsulating film, and the metal oxide layer is formed at the interface oflayers around the copper wiring and the copper anti-diffusion insulatingfilm.
 2. The method of claim 1, wherein the metal element doping layeris formed by doping a specific metal element by means of an implantationmethod or a plasma doping method, and the copper alloy layer is formedto have a thickness in the range of 10 Å to 500 Å, by controlling adepth and a concentration.
 3. The method of claim 2, wherein the metalelement doping layer is formed so that the concentration of the specificmetal element is in the range of 0.5% to 10%.
 4. The method of claim 2,wherein the specific metal element is a metal element such as Mg, Cd,Be, Sn and Pd.
 5. The method of claim 1, wherein the metal elementdoping layer is formed so that a concentration of a specific metalelement is in the range of 0.5% to 10%.
 6. The method of claim 1,wherein in order to remove a copper oxide layer generated on the surfaceof the copper wiring, a plasma treatment is performed in one of aprocess before the metal element doping layer is formed, a process inwhich the metal element doping layer is formed and a process after themetal element doping layer is formed.
 7. The method of claim 6, whereinthe plasma treatment is performed using a mixed gas of nitrogen andhydrogen or an ammonia series gas at a temperature in the range of 100°C. to 350° C.
 8. The method of claim 1, wherein after the secondinterlayer insulating film is formed, an annealing process for formingthe copper alloy layer and the metal oxide layer is performed.
 9. Themethod of claim 8, wherein the annealing process is performed at atemperature in the range of 100° C. to 500° C.